Power bank



FIG. 1 is a bottom, back, left side perspective view of a power bank,showing my new design;

FIG. 2 is a top, front, right side perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a back view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a right side view thereof;

FIG. 7 is a top view thereof;

FIG. 8 is a bottom view thereof; and,

FIG. 9 is a top, back, right side perspective view of the power bank,shown in an alternative configuration.

The broken lines shown in the drawings depict portions of the power bankthat form no part of the claimed design.

CLAIM The ornamental design for a power bank, as shown and described.